Isomerization of normal butane



Patented May 12, 1942 r 2,283,143 v rsomnnrza'rrou or NoaMALnUraNEVladimir N. was and Herman Pines, Chicago,

111., assignors to Universal Oil l'roductsCompany, Chicago, Ill., acorporation of Delaware No Drawing. Application Apr-i1 is, 1940, SerialNo. 330,314

9 Claims. v(oi. 260-676) This application is a continuation-in-part ofour co-pending application Serial No. 103,383, filed September 30, 1936.

This invention relates to the. treatment of butane of normal orstraight-chain structure.

In a more specific sense, the invention is concerned with a processwhereby normal butane is converted into iso-butane, the processinvolving the use ofspecial catalysts and particular conditions ofoperation which favor the isomerization reactions so that relativelyhigh yields oi'th iso-compound are produced.

Since the invention is concerned principally withthe two 4-carbon' atomparaflin hydrocarbons and their transformation, one into the other, thefollowing table is introduced to indicate the structure and theprincipal physical characteristics of these two compounds:

Properties of butenes Butanes are produced inconsiderable quantities inthe oil refining industry. They occur in substantial amounts in naturalgases (inwhich the normal compound usually predominates), in refinerygases which are evolved from crude sure of the other gasoline componentsto produce a gasoline of desirable starting characteristics ac-.

cording to seasonal demands.

The butanes at the present time bear a further important relationship tooil refining in that their excess production is being utilized as .asource of. gasoline either by ordinary thermal crackingor. by specialcatalytic dehydrogenation processes followed by polymerization in whichcatalysts may or may not be used. Investigations have shown thatiso-butane is considerably more amenable to cracking anddehydrogenation, both with and without catalysts, than the normalcompound. Considering the corresponding mono-olefins; the normal butenesare considerably more-difiicult to polymerize, either thermallyorcatalytically, than iso-butane,- and itis found also that the: octenesrepresenting the dimers of the iso-butene are of higher antiknock valuethan those from n-butenes which holds also for the octanes produced byhydrogenation. It is, therefore, of considerable importance at thepresent time: toconvert as much as possible of the normal butaneproduction into iso-butane, and the present invention is especiallyconcerned with a process'for accomplishing this object.-

- Critical 1 Name Structure B. P tirtcfirgagg Almos- 6'. pileresn-Butane CHaCHzCHrCHs. +0.5 15]. l 36 CH1\ i-Butanc ell-CH3" -10. 5 I34.5 37 on:

In one specific embodiment the present invention comprises the treatmentof normal butane for the isomerization thereof into iso-butane withcatalysts comprising aluminum chloride and hydrogen chloride at elevatedtemperatures and superatmospheric pressures.

We have determined that by the use of the types of catalysts mentioned,and particularly by. concurrent use of considerable superatmosphericpressure, normal butane may be converted into iso-butane with a yield ofas high as 60% to 65%.

petroleum storage tanks, and in the primary dis-. 7

tillation of crudes, and they are also present in considerablepercentages in the gases produced incidental to cracking heavy petroleumfractime for the production ofgasoline. In the case of cracked gasmixtures the relative proportions of iso and normal butanes vary,but'the ratio of the'iso to the normal compound is as a ruleconsiderably higher than in natural gas.

Butanes may be considered as more or less marginal compounds in respectto their desirability in ordinary gasoline, that is, a certainpercentage oi them is essential for sufiicient vapor pressure to insureease in starting, while an excess tends to produce vapor lock. For thesereasons the total percentage of 4-carbon atom hydrocarbons is commonlyadjusted in. conjunction with the boiling range and vapor pres-Evidently the use of superatmospheric pressures, of the order of 5-50atmospheres at temperatures within the range of approximately 80-200 0.,

besides depressing the volatilization of granular catalysts, tends alsoto depress numerous unde sirable side reactions which would resultin'the formation of hydrogen and low molecular weight. hydrocarbons, sothat the reaction proceeds more or less in one direction until anequilibrium is established.

There will be some amounts of aluminum chloride and hydrogen chloridewhich are best under the difierent temperature, and pressure rangesspecified, but as a.

rule, approximately 10% by weight of aluminum chloride and a minoramount of hydrogen chloride of the order of 1-2% by weight of thereactants will be used. The determination of the variations in" therelative I conducted by separately adding aluminum chloride, hydrogenchloride and normal butane to a comprises adding hydrogen chloride tothe normal closed pressure container, after which the container isagitated or the contents stirred mechanically while the temperature andpressure are raised by the application of external heat to produce atemperature corresponding to maximum production of the iso-compounds.This type of operation is better adapted to small scale production, andplants of. considerable capacity are best operated in a continuousmanner. In continuous operations the butane may be pumped through atubular heating element at a 7 given temperature and pressure within theap-;

proximate ranges previously specified and reaction brought about alongthe line of flow by the separate or joint injection. of proportionedamounts of aluminum chloride and hydrogen chloride. In the absence ofmoisture there willv be substantially no corrosionv when using thesesubstances. After passage throu h the heating element the reactants maybepa ed to enlarged insulated chambers for the completion of the desiredisomerization and the total products sub:- sequently fractionated torecover catalysts and separate the normal'and iso-'butanes, ,after whichthe normal compound may be re-cycled forfurther treatment.

Continuous operation mayalso be conducted.

by passing normal butane mixed with hydrogen chloride through beds ofheated granular aluminum chloride, either alone or mixed with carryingor spacing materials of a relatively inert character.

bon products andthe recycling of the hydrogen chloride for further use.

The following examples are,.introduced toindicate in a general way thenature of'thc results obtainable by the use of the process, though theyare not introduced with the intention of. correspondingly limiting thescope of the invention.

i'rrample I i 100 parts by weight of normal butane, parts by weight ofaluminum chloride and 2 parts by weight of hydrogen chloride wereintroduced funderia' pressure of about five atmospheres into a pressurevessel, which was then rotated and heated for twelvehours at an averagetemperatureof 150 C., the maximum pressure developed being about 30atmospheres. After thebomb was cooled the hydrocarbonswere released andfractionated and, it was found that they con-- sisted of 66.5%015iso-butane. and 31.9% of nor-1 mal butane. This indicates that theequilibrium 1underthese conditions is considerably in favor ofism-butane.

/ Example I I chloride and an amount of hydrogen chloride necessary toproduce about Satmospheres gauge pressure were placed in a pressurevessel and heated about 12 hours at 100C. 60.2% of isobutanewas producedfrom the n-butane charged with substantially no side reactions.

Treatment of the productswill in-, .volve merely the condensation of thehydrocarmy I p 7 2,283,143 v optimum ratios of n-butane and the catalystWe claim as our invention: 7 1. A continuous process for "producing highyields of isobutane from normal butane'which butane, passingtheresultant mixture through a bed of relatively inert carrier materialcontaining aluminum chloride under conditions such that isomerization ofnormal butane constitutes the principal reaction'in the precess,-'andseparating the resultant isobutane from the reaction mixture dischargingfrom the catalyst bed.

2. The process as defined in claim 1 further characterized in that thenormal butane is passedthrough the catalyst bed at an isomerizingtemperature below 200 C.

" A process for producing isobutane which comprises subjecting normalbutane, in the substantial absence of polymerizable olefins, to the Icomprises passin'g normal butanefa'ndhydrog'eh aluminum chloride, said!conditio I jecting the resultantmixture underisom chloride through areaction faoiie'jmaintained under isomerizing conditiorl s and ontainingamount of the hydrogen chlorid isomerization of normal .butan' principalreaction in the proces 6. A process for producing isobu ane m'n-ormalbutane which compnsesaaamg gaseous hydrogen chloride to thenormal butaneandpassing the resultantmi xture under isomerizing conditions through abed ofsolid-carrier material containing aluminum chloride, saidconditions and the amount of the hydrogenchloride being such thatisomerization of normal butane constitutes the principal reaction in theprocess.

7. A process for producing isobutane from normal butane which comprisesadding hydrogen chloride to the normal butane, and contacting theresultant mixture under isomerizing conditions with substantiallyanhydrous aluminum chloride supported on a solid carrier material, saidconditions and the amount of theh'ydrogen chloride being such thatisomerization of normal butane c onstitutesjth'e principal reactiontheprocess,' p

8. Theprocess as defined in claim 4 further characterized in. that saidconditions include an isomerizing. temperature below 200 Cf 9. A processforproducing isobutane from normal butane which comprises addinggaseousj' hydrogen chloride to the normal butane,, an' ubconditions totheaction of aisolid catalyst comprising substantiallyj anhydrousaluminum chloride-said conditions and the amount of the hydrogenchloride being such that isomerization oi normal butane constitutes the-.principal reacprocessy I ,.j.' V ,r. VLADIMIR N. IPATIEFF.

/ HEnMANrmEs.

